10+ netstat command switches with example – Unix/Linux

The “netstat” is one of the powerful command/tool to find out the network statics of your server. The “netstat” tool is available in both Unix and Windows OS. The word “netstat” stands for “Network Statics”. The “netstat” print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

>> Proto : The protocol (tcp, udp, raw) used by the socket.>> Recv-Q : The count of bytes not copied by the user program connected to this socket.>> Send-Q : The count of bytes not acknowledged by the remote host.>> Local Address : Address and port number of the local end of the socket. Unless the –numeric (-n) option is specified, the socket address is resolved to its>> canonical host name (FQDN), and the port number is translated into the corresponding service name.>> Foreign Address : Address and port number of the remote end of the socket. Analogous to “Local Address.”>> State : The state of the socket. Since there are no states in raw mode and usually no states used in UDP, this column may be left blank. Normally this can be one of several values:>> ESTABLISHED : The socket has an established connection.>> SYN_SENT : The socket is actively attempting to establish a connection.>> SYN_RECV : A connection request has been received from the network.>> FIN_WAIT1 : The socket is closed, and the connection is shutting down.>> FIN_WAIT2 : Connection is closed, and the socket is waiting for a shutdown from the remote end.>> TIME_WAIT : The socket is waiting after close to handle packets still in the network.>> CLOSED : The socket is not being used.>> CLOSE_WAIT : The remote end has shut down, waiting for the socket to close.>> LAST_ACK : The remote end has shut down, and the socket is closed. Waiting for acknowledgement.>> LISTEN : The socket is listening for incoming connections. Such sockets are not included in the output unless you specify the –listening (-l) or –all (-a) option.>> CLOSING : Both sockets are shut down but we still don’t have all our data sent.>> UNKNOWN : The state of the socket is unknown.

Important Files for “netstat” command:
The netstat command fetches details from the following file from your Unix server/machine.

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